MONTHLY PRECIPITATION SUMMARY
State of Hawaii portion of Honolulu HSA
MONTH: December 1998
PREPARED: January 4, 1999
State: No Flash Flood Warnings were issued for the state in December.
Urban and Small Stream Flood Advisories were issued for portions of
windward Oahu and Maui County on 28 Dec.
The period from 1 to 13 December was marked by very strong trade winds
that brought frequent but short-lived showers to the windward sections
of the island chain. These showers also arrived within the remnants
of old shear lines. An abrupt change of weather pattern occurred on
15 December with the passage of the first cold front of the 1998-99
cool season. This front was the first of three to push across the
island chain during the month. The second and third frontal passages
occurred on 28 December and 30-31 December, respectively. All three
fronts brought showers to the islands but did not cause significant
rain-related problems.
The late start to the 1998-99 cool season rains combined with the lack
of rain caused by the El- Nino episode during the first half of the
year resulted in most gages across the state having annual totals
below normal.
Island of Kauai:
The site at Wainiha was the only location to report higher than normal
rainfall (11.71 inches, 105 percent of normal). The Hanalei gage was
only slightly below normal with 9.09 inches, which is 94 percent of
normal. Both gages are located along north facing slopes of the
island and received most of their rain from showers carried by the
strong trades during the first two weeks of the month and during the
third frontal passage on 30 December. The rest of the gages reported
amounts about 40 to 80 percent of normal.
Island of Oahu:
Rainfall from the frontal passages at the end of the month helped
bring some relief to the dry leeward sections of the island. The
Lualualei gage observed 2.41 inches of rain with a cold front passage
on 31 December to bring the total for the month up to 2.89 inches (76
percent of normal). Many windward Oahu gages reported totals between
70 and 85 percent of normal. The Maunawili gage reported 10.21
inches, or 112 percent of normal. Most of this rain occurred during
the period of strong trades across the state. Once again, the Manoa
Lyon Arboretum topped all rain totals with 11.62 inches for December
(81 percent of normal).
December also brought to a close a very dry year for the Honolulu
Airport site. The annual total of 4.52 inches broke an all-time
record for low rainfall at that location (period of record 1947 to
present). The previous record of 5.03 inches was set in 1983, which
was also the tail end of a very strong El-Nino episode. However, a
major caveat is attached to this year's record. On 31 December, a
line of showers ahead of a cold front dropped 0.84 inches of rain
between midnight and 5:00 AM HST. The ASOS site that takes these
measurements subsequently failed and was out of service from 5:00 AM
to about 4:30 PM HST. Rainfall did occur at the Honolulu Airport
during this outage period, but backup observations did not note the
rainfall to be of heavy intensity with a significant restriction to
visibility. Another gage at Hickam Air Force Base, about 1.5 NM away,
reported 0.51 inches for the entire day.
Maui County:
December was quite wet for West Maui. Both sites along the windward
sections of West Maui (Kahakuloa, 6.10 inches, 117 percent of normal;
and Wailuku, 4.34 inches, 101 percent of normal) reported higher than
normal rainfall totals. As was the case with Oahu, the dry leeward
sides of Maui saw some relief with the rainfall associated with the
cold fronts. The gage at Kihei recorded 1.68 inches on 31 December to
bring the month's total up to 1.82 inches, or 76 percent of normal.
However, rainfall for all of 1998 remained very low at 2.62 inches, or
only 17 percent of normal.
Hawaii County:
Persistent and strong trades during the first two weeks of December
brought ample amounts of rainfall to the windward sections of the
island with many sites reporting amounts greater than 75 percent of
normal. Noteworthy sites include Mountain View, with 17.84 inches, or
110 percent of normal, and Glenwood, with 20.66 inches, or 120 percent
of normal. Gages in Kona, Kau, and South Kohala continue to indicate
a rainfall deficit with Pahala reporting 0.74 inches (14 percent of
normal) and Kamakoa reporting only 0.05 inches, or 2 percent of
normal.
BELOW ARE RAINFALL STATISTICS FOR SELECTED LOCATIONS FROM AROUND
THE STATE. THE FIRST COLUMN IS THE OBSERVED RAINFALL FOR DECEMBER.
THE SECOND COLUMN IS THE 30 YEAR AVERAGE FOR THAT LOCATION WHILE
THE THIRD COLUMN LISTS THE PERCENT OF AVERAGE RAINFALL FOR THE
MONTH OF DECEMBER.
KAUAI DEC AVG %AVG
LIHUE 2.16 5.2 42
HANALEI 9.09 9.7 94
HANAPEPE 3.37 4.3 78
OAHU
HONOLULU 1.15 3.8 30
MANOA ARBOR. 11.62 14.3 81
HAWAII KAI 1.76 4.1 43
AHUIMANU 7.02 10.9 64
WAIANAE 0.58 3.3 18
WAIALUA 4.08 5.0 82
MOLOKAI
KAUNAKAKAI 1.25 3.0 42
LANAI
LANAI CITY 2.28 4.6 50
MAUI
KAHULUI 1.16 3.2 36
HANA 2.05 6.1 34
KIHEI 1.82 2.4 76
LAHAINALUNA 1.57 3.4 46
WAILUKU 4.34 4.3 101
HAWAII
HILO 9.89 12.0 82
PAHALA 0.74 5.4 14
HONAUNAU 1.27 3.1 41
KAMUELA (UPPER) 2.91 6.0 49
KAMUELA 1.03 7.3 14
LAUPAHOEHOE 9.78 14.8 66
Data Sources: First order climate network weather observation stations
of the National Weather Service at Lihue, HI, Honolulu, HI, Kahului,
HI, and Hilo, HI. Additional data were taken from the Hydronet state
network of automated rain gages. Data collected in the automated
gages are not certified and information used above should be used for
information purposes only.
Kevin R. Kodama, Senior Service Hydrologist
National Weather Service Forecast Office
Honolulu, Hawaii